In the context of the developing market in so-called “bio” products, the big players among the major supermarket chains are turning to their suppliers, demanding products that fulfil these expectations.
These expectations are further increased as European directives require the progressive introduction of so-called “compostable” products that in particular satisfy the criteria set out in the European standard EN13432. In this connection, standard EN13432 specifies that the biodegradability of a product measured according to the released carbon-dioxide analysis method set out in EN ISO 14855 must be greater than 90%.
In the fields of packaging in general such as for example the closure of cans and cases, the assembly of cardboard trays, or in the more specific field of food packaging, adhesive compositions are commonly used for bonding printed papers onto any type of container, for food use or not, such as paper, bottles or pots, these containers sometimes being made from polystyrene, polypropylene, polylactic acid.
Customers' expectations in terms of compostable products are reflected at the level of the suppliers of each part of the packaging and customers require each of the components of a product to be biodegradable.
As a result, the supply of packaging items that are fully compostable or biodegradable therefore also involves the supply of hot-melt adhesive compositions that are compostable and/or biodegradable.
In this context, a hot-melt adhesive must also comply with said biodegradability standard EN ISO 14855 while retaining all of the other properties of a standard hot-melt adhesive, in particular the properties necessary for applying labelling to any type of container, for food use or not.
U.S. Pat. No. 5,312,850 describes the preparation of hot-melt adhesive compositions using certain ingredients known to be biodegradable. These compositions include 20 to 98% by weight polylactide (PLA) polymer containing at least 20% moles of lactide monomer, 2 to 80% adhesion-promoting resin having a softening point according to ASTM E 26 of approximately 60° C., 0 to 50% plasticizing agent and 0 to 30% wax as diluent and 0 to 3% stabilizing agent. No indication is given with respect to the biodegradability of the final composition according to standard EN ISO 14855.
WO 95/10577 describes the production of hot-melt adhesive compositions, preferably pressure-sensitive (hot melt pressure sensitive adhesives or HMPSA) called fully biodegradable/compostable by combining polyesters derived from lactic acid which are already known biodegradable polymers with biodegradable plasticizing resins based on polylactic acid (PLA), having a molecular weight less than 20,000 and having a Tg less than 60° C. No indication is given with respect to the biodegradability of the final composition according to standard EN ISO 14855.
These compositions containing PLA are not suitable for the fields of food packaging as they have the drawbacks of being rather stiff and having a heat-reactivation temperature that is too high for applications in the sought fields.
In the field of biodegradable hot-melt adhesive compositions without PLA, EP553394 describes the preparation of hot-melt adhesive compositions comprising a specific polyester obtained from 3-hydroxy-butyric and 3-hydroxy-valeric acid. No indication is given with respect to the biodegradability of the final composition according to standard EN ISO 14855.
EP 741178 also describes the preparation of hot-melt adhesive biodegradable compositions comprising a specific polyester obtained by reaction between a carboxylic diacid and a diglycidyl ether or ester. No indication is given with respect to the biodegradability of the final composition according to standard EN ISO 14855.
There is therefore a need to have available compostable hot-melt adhesive compositions capable of complying with European standard EN ISO 14855 and also fulfilling all the properties of a standard hot-melt adhesive, in particular the properties for applying labelling to any type of container, for food use or not.